Question

if the 80 people had eaten 100 kg rice in 20 days then 40 people eat 15 kg rice in how many days ?

Answer 1

100kg: 80 people =1,25kg eaten by each person in total
1,25kg :20 days=0,0625kg eaten a day by 1 person
15kg : 40 people=0,375kg will be eaten by each person
0,375kg : x days =0,0625kg
0,375=0,0625 * x /:0,0625
6=x
The answer is six days.

Answer 2

it is in compound variation
no of people    no of kg of rice       no of days
    80                       100                         20
    40                        15                           x
no of people and no of days are in inverse variation
no of kg and no of days are in direct variation
=80/40*15/100*20
answer = 6 days